1. Field of the Invention
The present invention relates to electrical connectors. More specifically, the present invention relates to the connector housings used in electrical connectors that are mounted to a substrate using surface mount techniques (SMT) such as ball grid array (BGA) technology.
2. Brief Description of Earlier Developments
Typically, the materials forming the housing of an electrical connector differ from the materials forming the substrate to which the connector secures. Materials used to make the connector housing can include high temperature plastics, such as liquid crystal polymers (LCP). Materials used to make the substrate can include thermosetting laminates such as FR4 glass-filled epoxy resin. In this example, and as is typical with most connector systems, the connector housing material has a different coefficient of thermal expansion (CTE) than the substrate material.
The effects of the mismatch in CTE differential occur during thermal cycling. During thermal cycling, the disparate materials expand and contract at different rates. The differential expansion and contraction introduces stresses at the junctions between the substrate and the connector. These stresses could reduce the lifetime of the connector or could possibly cause a fracture to the junction between the connector and the substrate.
Reducing the effects of CTE differential is an important consideration in connectors that utilize SMT, and in particular BGA technology. In particular because the fusible elements that secure the connector to the substrate serves as the primary electrical path between the contacts and the substrate.
It is an object of the present invention to provide an improved electrical connector.
It is a further object of the present invention to provide an electrical connector that reduces the effects of CTE differential.
It is a further object of the present invention to provide an electrical connector having a strengthened junction between the connector and the substrate to which the connector attaches.
It is a further object of the present invention to provide an electrical connector that limits the effects of CTE differential by manipulating certain features of the connector housing.
It is a further object of the present invention to provide an electrical connector in which certain characteristics of the connector housing are changed to limit the effects of CTE differential.
It is a further object of the present invention to provide an electrical connector with strengthened sections in preferential failure locations.
These and other objects of the present invention are achieved in one aspect of the present invention by an insulative housing for an electrical connector, comprising: a base; and at least one aperture extending through said base for receiving a contact. The aperture has an enlarged opening at one end adapted to receive a fusible element for securing the connector to a substrate. The enlarged portion has a cross-sectional area, in one orientation, that can be larger than the cross-sectional areas of other orientations.
These and other objects of the present invention are achieved in another aspect of the present invention by an electrical connector housing, comprising: a base; and a plurality of apertures in the base for receiving a contact. Each aperture has a recess for receiving a portion of a fusible element therein. Each recess has a characteristic, with the characteristic of a portion of the recesses being different than the characteristic of the other recesses.
These and other objects of the present invention are achieved in another aspect of the present invention by a method of limiting the effects of the differential coefficient of thermal expansion of an electrical connector and a substrate to which the connector mounts, comprising the steps of: providing an electrical connector with a housing having an array of recesses that receive fusible elements to secure the connector to the substrate; defining at least one predetermined location on the housing; and manipulating the recesses located in the at least one predetermined location.